Remote control system



26, 1938. P, CRAGO 2,124,651

REMOTE CONTROL SYSTEM VWL MRF-1 TSP l Y? v i LLL 1.95 196 @mw-5999M-V-Tfg" INVENTOR. Paul H. @Paga By i Q,

HIS A TT ORNE Y.

July 26, 193.8.A P, CRAGQ 2,124,651

' REMOTE CONTROL sYsTEM Y Filed Aug. :50, 1932 7 sheets-sheet 2 UFFSmaon C IV .INI/ENTOR. Paal @vago H15' ATTORNEY.v

July 26, 1938. P. H. cRAGo REMOTE CONTROL SYSTEM Filed Aug. 30, 1952 7Sheets-Sheet 3 /v INVENTOR. Pda( l/mgo ,Ewk

HIS A TT ORNE Y.

P. H. ciRAGo REMOTE CONTROL SYSTEM July 26, 1938.

Filed Aug. 43o, 1932 '7 Sheets-Sheet 4 July 26, 1938. p H- CRAGO2,124,651

REMOTE"CONTROL SYSTEM Filed Aug. 30 1952 7 sheets-sheet 5 Slow P450/i INVENT OR.

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July 26,31938. P H CRAGO 2,124,651

REMOTE CONTROL SYSTEM Filed Aug. 50, 1932 7 Sheets-Sheet 6- To Swidz QTFTSP

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l INVENTOR. TSP Paul H. Cmgo.

IIS A TTORNEY.

July 26, 1938. P. H. CRAGO 2,124,651

REMOTE CONTROL SYSTEM Filed Aug. 30, 1932 7 Shee'ts-Sheet'? [12d/minds@L gfza! @animi d L Signal [rad l? Signa! C012 tra( 12629720! lzzd. Y

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By Z

. H16' ATTORNEY,

Patented JulyA 26, 1938 UNITED STATES PATENT OFFICE REMOTE CONTROLSYSTEM Application August 30, 1932, Serial No. 631,041

73 Claims.

My invention relates to remote control systems, and particularly toremote control systems for controlling railway switches and/or signalsfrom a remote point such as a train despatchers ofce, and for alsocommunicating to said oflice the condition of said switches and/orsignals and other information, such as the presence of trains in thevicinity of the switches.

One feature of my invention is the provision,

1o in a system of the type described, of novel and improved apparatusthat permits the transmitting of different control influences from anoffice station to a eld station and the returning of differentindication iniluences from the field station to the oilice station overa single communieating channel or circuit. The method whereby thistwo-way control is accomplished over a single communication circuitconsists in providing loop circuits at the two stations each adaptableto pass current in a given direction only, and then causing control andindication currents to so flow in the communication circuit, eithersimultaneously or at time spaced intervals, that devices governed by theloop circuits are selectively energized. A further feature of myinvention is to provide a remote control system involving simple andrugged apparatus operating independently of marginal features as tocurrent, battery voltage balance or time of relay operation. Otherfeatures of my invention will become apparent from the followingdescription.

While many applications of my invention will naturally suggestthemselves to those skilled in the art, the specific applicationdescribed in the 35 present specification is that for controlling asingle railway switch and its related signals from an oflice station andindicating at the oflice station the condition of said switch andsignals, the communication channel in this instance consisting of oneline wire and a common return wire.

I will describe several forms of apparatus embodying my invention, andwill then point out.

the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a diagrammatic view of one formof apparatus utilizing alternating current for carrying out the controlprinciple embodying my invention. Fig. 1aL is a diagrammatic view of asecond form of apparatus whereby steady direct current is used forcarrying out the control principle embodying my invention. Figs. 2a, 2band 2c when taken together in the order named with Fig. 2a placed at theleft constitute a diagrammatic view of one form of apparatus embodyingmy invention wherein the control arrangement disclosed in Fig. l isapplied to the control of a single railway switch and its relatedsignals. Fig. 3 is a fragmental View of a modified form of apparatusthat may be employed at the eld station for storage of a switchoperating control influence. 5 Fig. 4 is a fragmental view of theapparatus at the eld station when modied to provide the returning of aswitch automatically to its former position in the event the switchpoints meet an obstruction which prevents the switch from 10 making acomplete movement from one position to the other. Fig. 5 is a fragmentalview of the apparatus at the iield station modified to include apolarized directional signal controlling relay which apparatus alsoembodies my invention. 15 Fig. 6 is a series of diagrams illustratingthe various forms of the impulses of the control and indication currentswhich are applied to the communication circuit when the controlapparatus takes the form disclosed in Fig. 1. Fig. 7 20 is a fragmentalview of a modied form of the field equipment that may be employed whenhand operation of the switch is to be permitted. In each of the severalviews like reference characters designate similar parts. 25

To simplify the figures as much as possible in order that they may bemore readily understood, I have in many instances illustrated a circuitcontrolling contact remote from the relay winding governing theoperation of that contact. In 30 all such instances the referencecharacter corresponding to the controlling relay is placed just abovethe contact and the contact is also given a distinctive individualreference character. For example, the circuit controlling contact ofFig. 35 2b designated by the reference character 20 is governed by arelay LAR of Fig. 2c to be fully described later, and this back contact20 is shown normally open inasmuch as the relay LAR is normallyenergized as will appear later in the 40 description. Y

Referring particularly to Figs. 2b and 2C, the reference characters land la designate the track rails of a stretch of railway track divided Dby the usual insulated rail joints to form a main 45 track section ITwhich contains a railway switch SW of the usual form leading to a sidingtrack PS. The track rails of the main track adjacent the track sectionIT are arranged to form a plurality of approach track sections 4T, A4T,5T 50 and A5T. Each of these approach track sections is provided with atrack circuit including a convenient source of current such as a battery2 connected across the rails at one end of the section and a track relaydesignated by the reference 55 character R plus a preX corresponding tothe section connected across the rails at the opposite end of thesection. The main track section IT is likewise provided with a similartrack circuit eXcept that its track relay ITS is normally held energizedby a stick circuit over its own front Contact 3. The pick-up circuit forthis track relay ITS includes the back contact 4 `.of a despatchercontrolled relay LGR and the back .contact 5 of a second despatchercontrolled relay RGR in series, both of which relays will be fully.

described later on. Associated with the track relay ITS is a slow-actingrepeater relay TSP', the energizing circuit of which includes the frontcontact 6 of the relay ITS, so that relay TSP is deenergized wheneverthe main track section IT is occupied. The repeater relay TSP is bothslow to release and slow to pick up, that is, it will not close itsiront contacts until its winding has been energized for somepredetermined time interval as well as its front contacts remain closedfor a given time interval after its winding is deenergized. The functionof relays ITS and TSP will 'appear when the operation of the apparatusis described.

Eastbound traic, that is, traiiic moving from the left to the right overthe switch SW is governed by signals designated by the referencecharacter R plus a suix A or B. Westbound traflic, that is, trafficmoving from the right to the left over the switch SW is governed by thesignals designated by the reference character L plus a sulix A or B, andthese two signals LA and LB are both mounted on a single mast. As isstandard practice an automatic distant signal RD governs eastbound traicapproaching the signal RA and an automatic distant signal LD governswestbound traflic approaching the signal LA. These signals may be of anysuitable form and as here shown' are the usual color light signals. Asis standard practice the signals RA and LA associated with traic on themain track are arranged to display a green light when tralic is toproceed and a red light when traflic is to stop. Signals RB and LBassociated with traffic moving to and from the siding PS are arranged todisplay a yellow light for traflic to advance and a red light when traicis to stop. The distant Y signals RD and LD will display green, yellowor red lights, green when the associated signal in advance is in theclear position, yellow when the signal in advance is at stop and redwhen the track section immediately in advance is occupied.

The operatingY circuit for each signal is governed by a signalcontrolling relay designated by the reference character H plus a prexcorresponding to the signal. Referring to the signal controlling relayRAH, when this relay is deenergized and its back contact I4 is closed,the circuit to the red light for signal RA is completed and when therelay is energized and its front contact i4 is closed, the circuit tothe green light of signal RA is completed. In asimilar manner each ofthe signal controlling relays of my system govern the operating circuitsfor-the associated signal. For the sake of simplicity the operatingcircuits for thedistant signals RD and LD are not shown as they form nopart of my invention.

The switch SW is adapted to be operated, as indicated by a dotted line,by the motor M of a switch machine SM Vof any of the standard types. Themotor M includes an armature 1 and a field winding il, and is controlledin part by means under the control of a despatcher at a remote office.As here shown the immediate control of the motor M, and thus of theswitch SW is accomplished by a polarized switchV controlling relay IWRwhich relay is jointly controlled, as will be described hereinafter, inaccordance with a control impulse transmitted from the destraiiic tomove to and from the siding PS, these contacts are moved to theirrespective dotted line positions.

Assuming the relay IWR to be energized, in a manner to befully`described hereinafter, with current of a polarity which I willcall reverse polarity, its polar armatures will be held in theright-hand position, that is, in a position opposite that shown in Fig.2C, to complete a reverse operating circuit for the motor M. Thisreverse operating circuit extends from the positive terminal B of abattery 41 through front contact 54 of relay IWR, right-hand contact ofpolar armature 55, Wire 56, armature 1, Wire 51, right-hand contact ofpolar armature 58, Winding 45 of a thermosensitive relay Rth to be laterdescribed, circuit controlling contact 9, eld winding 8 and to thenegative terminal N of the battery 41, closed the motor M rotates in adirection to actuate switch SW from its normal to its reverse position,the circuit being automatically opened at the circuit controllingcontact 9 when the switch is in the full reverse position. Assuming therelay IWR to be energized with current of a polarity which I will callnormal polarity, its polar armatures are held in the left-hand position,that is, in the postion shown in Fig. 2G, and current is supplied to anormal operating circuit for motor M. This normal operating circuitextends from the terminal B of battery 41 through front contact 54,left-hand contact of polar armatures 58,-

wire 51, motor armature 1, wire 5'5, left-hand contact of polar armature55, winding 45 of a second thermosensitive relay Nth, circuitcontrolling contact 9, assuming the switch SW to be in the reverseposition, field winding 8 and to the negative terminal N of the battery41. The direction of iiow of current in the armature 1 being now in thedirection opposite to that rst described, the

motor M is rotated in the reverse direction to operate the switch fromits reverse to its normalposition, this normal circuit beingautomatically opened at the circuit controlling Contact 9 when theswitch is in the full normal position. Thus it follows that with relayIWR energized with current of normal polarity the switch is set normaland when the relay IWR is energized with current of reverse polarity,the switch is set reverse. v

Associated with the circuit controlling contacts I 0, II, I2 and I3 is apolarized switch indication relay KR. With the switch SW normal, therelay KR is energized by virtue of a circuit that includes the Bterminal of battery 41, contact I3, left-hand contact of polar armature59 of relay IWR, winding of relay KR, back contacts 60 and 6I of relaysRWR and NWR, respectively, to be shortly described, contact I2 and tothe negative terminal N. The polarity of the current supplied by thiscircuit is such as to cause the polar armatures of the relay KR to beretained in the left- With this reverse operating circuit thusV YLiohand position. That is'to say, with switch SW in its normal position therelay KR is energized with current of what I will'call normal polarity.Taking the switch SW to be in'its reverse position, then current issupplied from the B terminal through contact I0, back contacts 6| and6U, winding of relay KR, right-hand contact of polar armature 59, andcontact to the negative terminal N. The direction of flow of current inthe winding of relay KR being reverse from that for the circuit firsttraced, the relay KR is energized with its polar armatures held in therighthand position. In accordance with the usual practice the winding ofthe relay KR is shortcircuited at the contacts Il), Il, I2 and I3Whenever the switch occupies any intermediate position as will bereadily understood by an inspection of Fig. 2C. It follows that relay KRis energized with current of normal polarity when the switch is normal,and with current of reverse polarity when the switch is reverse. It isto be noted that the relay KR is deenergized upon the energizing ofeither of the relays RWR or NWR so as to open either one of the backcontacts 6!! or 6|. Furthermore, it is to be observed that in order forthe relay KR to be energized there must exist agreement as to positionbetween the polar armature 59 of the relay IWR and the circuitcontrolling contacts |U, |2 and |3.

Still referring to Figs. 2b and 2U, RAR is an approach relay associatedwith eastbound traffic, the circuit for which is controlled by the frontcontacts I6 and of the track relay 5TR and the front contacts |8 and I9of the track relay ATR of the approach sections 5T and AST,respectively. In like manner the approach relay LAR is associated withwestbound traffic and its circuit includes front contacts 2| and 22 oftrack relay 4TR and front contacts 23 and 24 of track relay AdTR for theapproach sections 4T and AAT, respectively.

The reference character RMR designates the usual approach locking relayassociated with eastbound traffic. The manner of controlling theapproach locking relay RMR may be in accordance with any of severalmethods commonly used, but as here shown it is normally retainedenergized by a stick circuit that extends from the positive terminal Bof a convenient source of current such as a battery not shown, backcontacts 25, 26 and 2T of signal controlling relays RDI-I, RBH and RAH,respectively, its own front contact 28, winding of relay RMR and to thenegative terminal C of the same source of current. Relay RMR is providedwith a pick-up circuit that includes three branch paths around its ownfront contact 28. One path includes a contact 29 actuated by the switchSW and closed only when the switch occupies its normal position, and thefront contact 3l) of the approach relay RAR. The second branch pathincludes the back contact 3| of the opposing approach relay LAR and theback contact 32 of the track repeater relay TSP. The third branch pathincludes the front contact 33 of a time element relay TE to be describedlater. It is clear that when any one of the signal controlling relaysRAI-I, RBI-I or RDI-I is once energized to clear its associated signal,the stick circuit for the approach locking relay RMR is opened and thatrelay deenergized after which it can be reenergized only when the signalcontrolling relays are all down and one of the branch paths mentionedabove is closed.

Associated with westbound traffic is the approach locking relay LMR thatis normally retained energized by a stick circuit similar to thatdescribed for the relay RMR and which includes the back contacts 34, 35and 36 of the signal controlling relays LDH, LAH and LBI-I,respectively, and its own front contact 31. The pick-up circuit for theapproach locking relay LMR includes three branch paths around its ownfront contact 3T. The first path includes the front contact 38 of theapproach relay LAR, the second path includes the back contact 38 of thetrack repeater relay TSP and the back Contact 45 of the opposingapproach relay RAR in series, there being a contact 29a, operated byswitch SW and closed only when the switch is in its reverse position,arranged in parallel with the contact 40. The third path includes thefront contact 4| of the time element relay TE. Thus, the approachlocking relay LMR is deenergized whenever any one of the signalcontrolling relays associated with westbound traffic is picked up andonce the relay LlVIR is deenergized it can be again picked up only whenthese signal controlling relays are all down and one of the branch pathsjust mentioned is closed.

Associated with these two approach locking relays RMR and LMR is a relayMP. The relay MP can be supplied with current by either one of twocircuits. Assuming relay LMR to be deenergized, a circuit is completedfrom the terminal B at a signal location LD, through back contacts 34',35 and 36 in series, back contact 31 of the relay LMR, wire 42, windingof relay MP to the negative terminal C. With the relay LMR picked up butthe approach locking relay RMR down, a circuit is closed from theterminal B at the signal location RD through the back contact 25, 26 and21 in series, back contact 28 of relay RMR, wire 43, front contact 44 ofrelay LMR, wire 42, winding of relay MP to the terminal C. Whenever therelay MP is energized, current is supplied by a simple circuit to thewinding of the time element relay TE. While relay TE may be any one ofseveral different types of time element devices, it is here shown as arelay that closes its front contacts a predetermined time interval afterits winding is energized and has a check contact to be referred to laterwhich is closed in the deenergized position of the time element device,but opens when the relay is first energized. As stated above, the mannerof controlling the approach relays RAR and LAR, the approach lockingrelays RMR and LMR, the relay MP and the time element device TE may beany one of several customary schemes employed in systems of the typehere involved, and the form here shown for the control thereof is onlyone of the several alternative forms that may be employed.

The polarized switch controlling relay IWR is normally deenergized andis of the type that its polar armatures remain firmly held in theposition to which they were last moved during the time the relay isdeenergized. Not only is this relay normally deenergized but its windingis normally short circuited as an extra precaution against a falseoperation and also to give the relay slow release characteristics undercertain operating conditions as will later appear. To be explicit, oneterminal of the winding of relay IWR is connected directly to the centerC connection of battery ll and its other terminal is normally connectedthrough a circuit network including front contacts 48, 49, 56 and 5| ofrelaysk RMR, LMR, ITS and TSP, respectively, wire 52, contact 'lll-65 ofcontinuity transfer contact B2 to be later described of relay RWR,contact '|6-65 of vcontinuity transfer Vcontact Blof relay NWR,

4front contact 53 of the switch `indication relay .'KR'and thence to thecenter C connection of battery 41. For the actual control of the switchcontrolling `relay IWR, I provide two neutral relays RWR andV NWR andvtwo thermosensitive relays Nth and Rth, each of the latter beingprovided with a heating element 45 and a contact 46 controlled thereby.The relays RWR and NWR are normally deenergized and Vare under thecontrol of therdespatcher at the remote office as will shortly appear.When the relay RWR is selected, a circuit is closed for energizing therelay IWR with current of normal polarity. When the relay NWR isselected, a circuit is closed to supply current of reverse polarity tothe winding of the relay IWR. Assuming relay NWR to be selected, thecircuit for relay IWR eX- tends from the N terminal of battery 41through contact 46 of the thermosensitive relay Rth, resistance 69, wire18, front contact I of continuity transfer contact BI of relay NWR,contact 1li-65 of continuity transfer contact B2 of relay RWR, wire 52,front contacts 5l, 5D, 49 and 48 .in series, winding of relay IWR and tothe center C connection of the battery 41. As stated above, I haveelected that the current supplied by this circuit is of reverse polarityand thus the polar armatures of the relay IWR will be shifted to theright-hand position. While there normally existed a short tcircuitingpath from the back contact 65 of relay NWR through the front contact 53of the relay KR, it is to be noted that whenever the relay NWR isselected, this Vshort circuit path is ruptured first .at the backcontact 65 and then later at the front contact 53 of relay KR, due tothe fact that the relay KR is deenergized by the opening of the backcontact 6l as the relay NWR picks up. For purposes to later appear,relaysNWR and RWR are preferably pivoted with continuity transfercontacts BI and B2, respectively. In each contact B-I and B2 the uppermember 10 serves as a transfer element, the middle element 65 serves asa back contact which mates with the transfer element during deenergizedperiods lelement and the back contact 65 can be broken.

vOnce the relay I WR is energized by the selecting of the relay NWR aspointed out above, a stick circuit is provided to hold the relay IWRenergized after the relay NWR drops. This stickvcircuit branches fromWire 18 along the wire 66, right-hand contact of its own polar armatures68, front contact 61, contact -65 of contact Bl of relay NWR, assumingthis relay to be now deenergized, contact 10-65 of contact B2 of relayRWR, wire 52, front contacts 5|, 50, 49 and 48, winding of relay IWR andto the center C connection of battery 41. Thus, the energizing of VrelayN WR for a relatively short period of time in a manner to be laterdescribed, will open the normal short circuit on the winding of therelay IWR, and supply to that relay, current of reverse polarity causingits polar armatures to be shifted to the reverse position, and it willalsoV deenergize the switch indication relay KR. Once energized withcurrent of reverse polarity the relay IWR is provided with a stickcircuit Vto retain that relay energized after the relay NWR has becomedeenergized. Inconnection with the deenergizing of relayNWR, it is to benoted that theY energizing of the relay IWR with currentof Y reversepolarity causes the motor M to operate the switch from its normalpositiontoits reverse position. When the switch SW is fully reversed, Ythe reverse circuit for the relay KR is completed and relay KR is againpicked up, assuming relay NWR to be now deenergized as will appearlater. The closing of front contact 53 of relay KR closes the shortcircuit to the winding of relay IWR and that relay becomes deenergized,releasing its neutral armatures with a slow release action but, however,retaining its polar armatures in the reverse position. It follows thatthe applyingY of current of reverse polarity to therelay IWR iscontrolled in part by the relay NWR and in part by the circuit networkcontrolled by the relays RMR, LMR, ITS-and TSP, which relays areresponsive to traffic conditions as described hereinbefore.

Selecting the relay RWR, opens the circuit to the relay KR at its backcontact 60, opens the short circuit for the winding of relay IWlRl atthe back contact 65 of contact B2 and closes an energizing circuit forthe relay IWR that can be traced from the positive terminal B of thebattery 41 through contact 46 of the thermosensitive relay Nth,resistance 63, wire 64,front contact l5 of contact B2 of relay RWR, wire52, contacts 5|, 50, 49 and 48, winding of relay IWR and to the center Cconnection of the battery 41. The polarity of the'current now suppliedto Vthe Winding'of relay I WR is of normal polarity and the polararmatures of relay IWR are shifted to their normal positions. 'I'hestick circuit for relay IWR now extends from wirev 64 through theleft-hand contact' of polar armature 68, front contact 61, contacts10-65 of both BI and B2 and thence as before traced through the trafficcontrolled circuit network and the winding of relay IWR to the center Cconnection of battery 41. Relay RWR being provided with continuitytransfer contact B2, the relay IWR when picked up in response to theselecting of the relay RWR for a short period of time is retainedenergized `over its stick circuit after relay RWR becomes deenergized;With relay IWR energized with current of normal polarity the motor Mactuates the switch to its normal position and when the normal positionis thus reached, the circuit for supplying the relay KR with current ofnormal polarity is completed Vassuming relay RWR is now deenergized aswill later appear. As relay KR picks up, the short circuit for thewinding of relay l WR will again be closed at the front contact 53 ofrelay KR and relay IWR will become deenergized Yreleasing its neutralarmatures with a slow-release action, but retaining its polar armaturesin the left-hand position.

To sum up, the selecting of the relay NWR for a short period of timeVremoves the short circuit on the relay IWR, deenergizes the KR relayand energizes relay lWR with current of reverse polarity providingtrafhc conditions are normal.

When the switch is fully reversed, the lrelay KR is again picked up andthe short circuit from relay IWR is again closed causing it to be slowlyreleased. When the switch SW is in its reverse position and relay IWRreversed, the selecting of the relay RWR for a short period of timeopens the short circuit on relay IWR, deenergizes the KR relay andsupplies the winding of relay IWR with current of normal polarity. Whenthe switch is full normal, the short circuit for relay IWR is againclosed to cause the relay IWR to be slowly released.

In the event the polar armature 'Il of relay IWR occupies its left-handposition due to the fact that that relay was last energized with currentof normal polarity, the relay NWR is prepared to be selected by thedespatcher at the remote office. The local circuit for selecting relayNWR includes the terminal B of the current source, front contacts 'l2and 73 of the despatcher controlled relays LGR and RGR, respectively, tobe controlled in a manner to be shortly described, wire 14, left-handContact of polar armature 1|, back contact 'I5 of relay RWR, winding ofrelay NWR, to the terminal C of the same source of current. During theinterval the despatcher controlled relays LGR and RGR remain up afterthe polar armature 'H has been shifted to its` righthand position due tothe energizing of relay IWR with current of reverse polarity the relayNWR is provided with a stick circuit branching from the wire 'I4 alongwire 16, front contact 17, winding of relay NWR to the terminal C. Inthe event the polar armature 'il of relay IWR occupies its reverseposition due to the fact that the relay EWR was last energized withcurrent of reverse polarity, to move the switch to its reverse position,the energizing of the despatcher controlled relays LGR and RGR to closethe front contacts l2 and 'I3 completes a pick-up circuit for the relayRWR. This circuit extends from terminal B through iront contacts 12 and13, wire 14, the right-hand contact of polar armature 1|, back Contact79 of relay NWR, and winding of relay RW R to terminal C. Relay RWR isprovided with a stick circuit that branches around the polar armature 'Hand the back contact "I9` and which includes its own front contact 86 toretain this relay energized during the interval the relays LGR and RGRremain picked up after the polar armature 1| has been shifted to theleft due to the supplying of current of reverse polarity to the relaylWR. It is. to be seen, therefore, that when relay IWR is leftdeenergized with its polar armatures occupying the normal positionindicating that the switch is invits normal position, the energizing ofthe two despatcher controlled relays LGR and RGR selects the relay NWRto apply current of reverse polarity to relay IWR to bring about thereversing of the switch. The relay NWR once selected, it is then heldenergized as long as. the relays LGR and RGR are picked up in responseto a control impulse from the despatchers loiirlce to prevent theselecting or the opposing relay RWR after the relay IWR hasbeenreversed. When the relay IWR is left deenergized with its polararmatures in the reverse position indicating that the switch is in thereverse position, the energizingl of the two despatcher controlledrelaysLGR and RGR selects the relay RWR to supply current of normal polarityvto the relay IWR to bring about the movement of the switch to itsnormal position. Relay RWR once selected it is held energized by a stickcircuit to prevent the selecting of the relay NWR after the polararmatures of relay lWR have been shifted to the normal position.

To sum up the control of the switch SW, the

switch controlling relay IWR is normally deenergized with its polararmatures. occupying the position corresponding to the position oi theswitch. That is to say, with the switch normal, the relay IWR isdeenergized with its polar ar.- matures normal and with the switchreverse the polar armature of relay iWR are in the reverse position, andinaddition, the winding oi the relay IWR is normally short-circuited.With relay IWR in its normal position the energizing of the twodespatcher controlled relays LGR and RGR selects the relay NWR which, asit becomes energized opens the short circuit, deenergizes relay KR andapplies to the relay IWR current of reverse polarity to bring about thereversing ci the switch. When the switch is in the full reverseposition, the switch indication relay KRis again` picked up closing theshort circuit of relay IWR and thereby causing the relay IWR to beslowly released. With relay EWR in its reverse position,

the selecting of the two despatcher controlled relays selects therelay'RWR which as it becomes energized opens the short circuit,deenergizes relay KR, and applies current of normal polarity to therelay WR to bring about the moving of the switch to its normal position.As the switch reaches its full normal position, the KR relay is againpicked up closing the short circuit and slowly releasing the iWR relay.Whichever relay RWR or NWR is iirst selected, that relay remainsenergized during the entire interval that the despatcher controlledrelays are energized which interval, as will appear later, is ordinarilymuch shorter than the time required for a movement of the switch.

Having described in detail the local control circuits for the operationof the switch SW, I

will next take up the local control circuits for the I-I signalcontrolling relays. Assuming the switch SW to be in its normal positionand referring to the signal controlling relay RAI-I for the eastboundsignal RA, this relay is provided with a oircuit that can be traced fromthe positive terminal B of the current source through the check contact8l and back Contact 82 of the time el-ement relay TE, front Contact 8Sof relay TSP, front contact 84 of relay KR, normal contact or" polararmature 85 of relay IWR, normal contact of polar armature 86 of relayKR, back contact 81 of the despatcher controlled relay LGR, frontcontact 88 of the westbound approach relay LAR, winding of relay RAI-I,front contact 89 of the despatcher controlled relay RGR to the terminalC. It follows that with the apparatus in the position shown in theiigures, the above-traced circuit for the relay RAI-I can be closed bythe energizing of the despatcher controlled relay RGR. The circuitnetwork for the signal Vcontrolling relay LAI-I for the opposingWestbound signal LA is the same as that just traced for the relay RAI-Iup to the polar armature 86 of relay KR thence it extends along the wireQ9, front contact 9| of the despatcher controlled relay LGR, frontcontact 92 oi the eastbound approach relay RAR, Winding of relay LAI-I,back Contact 930i relay RGR, to the terminal C. As this circuitisnormally completed except at the 'front contact il! of the despatchercontrolled relay LGR, it follows that relay LAH will be energized andsignal LA cleared by the energizing of the despatcher controlled relayLGR. Recalling that When the switch SW is in the reverse position, thepolar armatures of the relay IWR occupythe reverse position and that therelay KR is energized in -its reverseposition, the signal controllingrelay RBI-I for the westbound signal RB is provided with a circuitnetwork that extends from the terminal B of the current source over thesame circuit previously described up to the polar armature 85 of relayIWR thence by the reverse contact of polar armature 85, reverse contactof polar armature 94 of relay KR, back contact 95 of relay LGR, frontcontact 96 of relay LAR, winding of relay RBH, front contact 91 of relayRGR to the terminal C. That is to say, when the switch SW Yis set'fortraffic to the siding PS, the relay RBH will be energized to clearV thesignal RB by the picking Vup of theV despatcher controlled relay RGR.Again, with the switch SW in its reverse position, the signalcontrolling relay LBH for the westbound4 signal LB is provided with acircuit network that extends from the terminal B, the same as justdescribed up to the polar armature 94 of relay KR, thence over Vwire98,v front contact 99 of relay LGR, front Contact |00 of the approachlocking relay RMR, winding of relay LBH, back contact |0| of relayARGRto the terminal C. That is to say, with the switch set for the siding,the energizing of the despatcher controlled relay LGR to close its frontcontact 99 completes a circuit to the relay LBH for clearing the signalLB.

It will be noted that the signal controlling relay RDH for the distantsignal RD is governed by a circuit easily traced that includes the frontcon- Y Vtact |02 of the signal controlling relay RAI-I for Yergizing ofan associated despatcher the signal RA. In like manner the circuit forthe relay LDH that governs the distant signal LD is controlled by'asimple circuit that includes the r,front contact |03r of the relay LAI-Ifor the signal LA. In any event to retain a signal controlling nalsassociated therewith it is seen that the switchV operates from anyposition it may happen to be,

to an opposite position by theV energizing of the two despatchercontrolled relays simultaneously for a brief interval of time, but toretain a signal in the clear position requires the continuousencontrolled relay` Y Referring now to Figs. 2a and 2b and moreespecially to Fig. l, I provide a communication channel whichv includesa pair of line wires designated by the reference characters. L and Cormbetween the office station and the eld station. It will be understoodthat in practicing my invention a single office station in charge of adespatcher er will most likely have jurisdiction over several eldstations located along the railway vand the line wire Com will act as acommon return wire for all stations. In this form of apparatus, of myinvention a source of alternating current is provided at both the officestation and the eld station. As'shown in Fig. l both the oflice stationand the field'station are normally supplied with current by a linetransformer T each of which has its primary winding |04 permanentlyconnected to the transmission wires |05 and |00 supplied withalternating current from a generatorY |01. The CX terminal of thesecondary, |08 of each of the line transformers is directlyrconnected tothe common return wire Com. The BX terminals of the secondaries |08 Vareconnected to the line `wire L through the apparatus at its location aswill appear as the specification progresses. Considering a given instantthe terminal BX of each transiformer will be positive andthe CX terminalnegative Vand then upon the next instant the BX terminals will benegative and the CX'terminals positive.

'Ihe office station is provided with a manually operated signalcontrolling lever LV and a man`v ually operated switch controlling pushbutton PB.

The lever LV is capable of being moved to any one of three restingpositions designated by the reference characters n, l, r, and operates aseries of circuitcontrollersRI, Ll, BD, R2 and L2 (see Fig. 2a). Thebridging piece |09. of controller BD engages both' the contact springs||0 and when the lever LV is in its n position and is rotated out ofcontact with these springs when the lever is moved to either its r or Z.position. The bridging piece I |2 of controller L1 spans both thecontact springs ||3 and ||4 when the leverv LVv is moved to its Zposition only, and the bridgingV piece 5 of controller RI spans 'contactsprings ||0 and ||1 when the lever LV occupies its r position only. In asimilar manner connection is.

made between the Asprings |55V and |56 of controller R2 by bridgingpiece 214 when the lever LV to its r position, and connectionris madebetween the springs |53 and |54v of controller L2 by bridging piece 215when the lever LV is moved to its Z position.

Associated with the push button PB is a slow release relay PBR. The pushbutton PB is of the spring return type and in itsnorrnal position4ensofi gages a front contact ||8Ywhere it completes a Y' short circuitfor the Windi-ng of relay PBR as will be readily understood by aninspection ofY Fig. 1. When the push button PB is depressed to engagethe back contact ||9 the short circuit to theV winding of relay PBR isremovedY and that relay supplied with current from the'positiveterminalB of a convenient source through back contacts |60 and |6| (see Fig. 2a)of control relays- LKP and RKP, respectively, to be described later,contact ||0||| of controller BD, contact ||9, winding of relay PBR,resistance |20 and to the opposite terminal C of the same source ofcur-V rent. Asv longY as the relay PBR is energized and closes its frontcontact |23, the BX terminal of the secondary |08 is connected to theline wire L and thus it follows that the full wavecf the alternatingcurrent supplied by the transformer T at the oce station is applied tothe ,communif cation circuit. At the field station there is provided(see Fig. l) two despatcher controlled re-` -opposite direction. Theotherterminal of relay RGR is connected to theline wire Com through ahalf wave rectiern|29 which is so positioned in the circuit that itfreely passes Vcurrent flowingv from the relay towards the common returnWire and substantiallyprevent-s theflow ofA current in the oppositedirection. While these rectiers as well as all other rectiiiers employedin my system may be any one of many types, a preferred type is thatdisclosed and claimed in the United States Letters Patents No.1,640,335, granted to L. O.

Grondahl, Aug. 23, 1927. It follows, that the full wave alternatingcurrent applied to the line wires L and Com at the oilice station duringthe period the relay PBR is energized will cause both relays LGR and RGRat the :lield station to become energized, on-e of the half wave pulsesof the alternating current owing through the loop circuit including therelay LGR and rectier |28 and the other half wave pulses vof thealternating current flowing through the loop circuit including the relayRGR and rectier |29. As will appear hereinafter, the simultaneousenergizing of these two control relays LGR and RGR is utilized forgoverning the operation of a railway switch.

In order to clarify the description I shall at times speak of currentowing inthe line wire L from the oice station towards the eld station ascurrent of positive polarity, and current flowing in the-oppositedirection in the line wire L, that is, from the eld station towards theoilice station as current of negative polarity. Thus, the momentarydepressing of the push button PB picks up relay PBR and pulses ofcurrent alternately of positive and negative polarity are Asupplied tothe communication circuit during the release period of the relay PBR forsimultaneously controlling the relays LGR and RGR.

The BX terminal of the secondary |08 at the oice station is connected tothe contact spring ||1 of controller RI through a half wave rectier |2|and to the contact spring ||3 of controller LI through a half waverectifier |22. The rectifier |2| is so positioned in the circuit that itreadily passes current flowing from the BX terminal toward the springWhile substantially preventing the flow of current in the reversedirection. As the spring ||6 of controller RI is connected directly tothe line wire L, it is clear that when the lever LV -is moved to its T,position and the contact ||6| I1 closed, pulses of current of positivepolarity are supplied to the communication circuit which flows out theline wire L through relay RGR, rectier |29 and back over the commonreturn wire Com. At the oiiice station there are provided two controlrelays LKP and RKP each having one terminal of its winding connecteddirectly to the common return wire Com. The other terminal of thewinding of relay LKP is connected through a half wave rectier |26 andthe back contact |25 of relay PBR to the line wire L. The rectiiier |26is so positioned that it freely passes current ilowing only from theline wire L toward the relay LKP. The other terminal of the winding ofrelay RKP is connected to the line wire L through a half wave rectier|21 which is so positioned as to freely pass current flowing only fromthe relay toward the line wire L. Thus when lever LV is moved to its 1"position and half wave pulses of current to positive polarity aresupplied to the line circuit as stated above for energizing the relayRGR at the eld station, positive half wave pulses of current will alsopass through the rectier |26 to energize the relay 'LKR Rectiiier |22 isso connected in the circuit as to pass current flowing from the spring||3 toward the BX terminal of the secondary |08, that is, in a directionreverse to that of rectifier |2|. As the spring ||4 of controller Llisconnected directly to the line wire L, it follows that half wavepulses of current of negative polarity will iiow out the common returnwire Com, through rectiiier |28, relay LGR and back over the line wire Lwhen the lever LV is moved to its Z position and that negative halfpulses of current will also ow through the relay RKP and the rectier |21to energize that relay. Thus, when the lever LV is moved to its rposition, pulses of current of positive polarity are supplied to thecommunication circuit and the relay LKP of the oiice station and therelay RGR of the eld station are both energized. When half wave pulsesof current of negativey polarity are supplied to the communicationcircuit in response to the lever LV being moved to the Z position, therelay RKP at the oice station and the relay LGR at the eld station areboth energized. That is to say, the operation of the push button PBcauses a full wave alternating current to be applied to thecommunication circuit which current circulates through the two loopcircuits at the eld station to energize the relays LGR and RGRsimultaneously. The two control relays LKP and RKP at the olice stationremain deenergized at this time due to their circuit being held open atthe back contact |25 of the relay PBR. Operating the signal lever LV toeither its l or r position causes half wave pulses of alternatingcurrent to be applied to the communication circuit which circulatesthrough the corresponding loop circuits of the eld and oflice stationsin parallel. As shown in Figs. 2a and 2b, half wave rectiers |92 and |93may be connected across the terminals of the relays RKP and LKP,respectively, and the half wave rectiers |9| and |94 may be connectedacross the terminals of the relays LGR and RGR,- respectively, causingthese relays to be operated on a much lower voltage and causing them tober somewhat slow releasing in character.

As stated at the outset of this description, the indicating of thecondition of the apparatus at the eld station is accomplished over thesame communication circuit as is used to transmit the control energyfrom the ofce station to the eld station. As shown more clearly in Fig.1 the secondary |08 of the transformer T at the iield station has its CXterminalconnected to the common return wire directly and its BX terminalconnected to the line wire L through either one or the other of two halfwave rectifers and 13|, a polar armature |89 of the indication relay KR,and a series of circuit networks indicated only in Fig. 1 but to bedescribed in detail in connection with Fig. 2b. As will appear when theoperation of the system is described, the

relay KRV together with the circuit networks indicated in Fig. 1 are sogoverned that the supply'of indication current from the fieldtransformer T to the communication circuit is such that, at such time aswhen the control current ows from the oflice station out over the linewire L and back over the common return wire, the indication current ismade to flow from the eld station toward the oflice station over thecommon return wire and return over the line wire L. At such time as thecontrol current flows out over the common return wire and returns overthe line wire L to the oiiice station the indication current is made tollow from the field station over the line wire L and return over thecommon line wire. In other words, the two remotely located stations ofFig. 1 are connected by a single control circuit provided with a pair ofloop circuits at each station each of which is isf adapted to pass;current in one direction only. Each station is supplied with alternatingcurrent from a common source from which currentA is made at times toflow from each station in 5 the control circuit in the same direction attime Y spaced intervals equal to one-half cyclev of the alternatingcurrent, whereby a loop circuit at each station is energized by thecurrent supplied at the opposite station.

Referring now to Fig. 2a there is provided at the oilice station anormal switch indication, lamp |32 and a reverse switch indication lamp|33 vvhichVV are associated with a normal: switch indication: relay NWEand a` reverse switch indication'relay RWE, respectively. The normalindication relay NWE is shown held energized by virtue ofY a stickcircuit extending from the B terminal ofk the source of current, backcontact- |34fof relay PBR; front contact |35 ofl relay 20 NWE,backcontact |361 of relay RWE, Winding of relay NWE to the terminal C ofthe current source. The indication lamp |32. being' connected inparallel with the Winding of` relay NWE, this lamp, is displayedWhenever the relay is enby its stick circuit', it can loe picked up onlyWhen'thecontrol relay LKPis energized` to close its front Contacty |31which is in parallelvvith the' front contact |35 of relayN WE. Thereverseswitch-indication relay RWE-'is provided'with a;

pick-upf circuit that includes the terminal B, back contact |34, frontcontact |38 kof the` controlv relay RKP,A back 'contact |39 of relayNWE, Winding-of 'relay RWE to the terminal C, while w ,the indicationlamp |33-is connected in parallel with its Winding. `The stick circuitfor' relay RWE includes itsovvn-irontY Contact |40 in parallel with `thefront Contact |38 of control relayl RKP.A In addition'vto'the relays NWEand RWE 40% governing the 'switch indication lamps, they also governatVtheir front contacts YHH `and |42, respectively, the connection''betweenthe'BX terminal of the secondaryv |ll8- andY the rectifiers |2|and |22;

be completed to supply asigna] controlling cru"-V renttothecommunication. channel. i Associated -with the signal controlling leverLV areithree signal ,indicationlamps normalV lamp |43,V L signallainp|44 and R signal lampl |45;

minal B through theback Contact |49l of'relay RKPJv-ire |50, lamp|43,'Wire |5|, back contact |52of-relay LKP to the terminal lC;Normally, the relay HKP has one terminal of its winding oaconnected toterminal C throughl the back contact |46 of control'relay LKP-,anditsopposite' terminal also connected to the C terminal throughVv theback-contact- |47 'of' the control relay RKP.- Whenever relay LKPbecomesV engergized in a manner to later'appear to closeits frontcontact |46, current 4issupplied to 'the-v Winding of relay HKP Whichflows through the Windingin a direction Vto shift ther polar armature|48of that relay toits right-hand position,

rg that is, to -theposition opposite to that shown in Fig. 2a. Thepicking upiof'the controlrelay RKP to close the front contact |41supplies current tor-the Winding of relay HKP that'ilows in the windin-gof vthat relay in a direction to shift ;,the polarfarmatureY |484 toitsleft-hand posiergized. While relay NWE is retained energized'lltfollowsthateither one or theY 451-: other of these switch indicationrelays must be energized'before a signal controlling circuit can" tionthat is, to the position shown in Fig. 28V;

to its left-hand position. Under this conditionvv ofV theY oice stationequipment the subsequent energizing of the controlrelay LKP completes,

a circuit from the B terminal through front contact |49 of relay'R-KP,left-handrcontact of polar armature |48 of relay HKPflamp |44, contact|53|54 of controller L2, iront contact |52 of relay LKP to the terminalC with the result that the' L signal indication lamp |44 will beilluminated. Placing thelever LV at its 1^ position' so that'half-wavepulses ofpositive polarity are suppliedY to thecontrol circuit and'tothe local loop'circuit, the control relay VLKP is Yenergized which willextinguish the normal signal lamp Y |43 and shift the relay HKP toitis'right-hand position. Y Under thisv condition ofthe oilice'ap-Yparatusthe subsequent energizing ofthe control relay RKP closes thecircuit from terminal B through ther'front contact |49- of relay RKP,

right-hand contact of polar armature |48, lamp- |45, contact ISE-|56 ofcontroller R2,fandthe front contact |52 ofV relay-LKP tothe terminal Cwith the resultf that' the R signal indication lamp |45 willbe'illuminated. It is t'o be seen, therefore, th'at'with the lever LV initsv normal position andboth control relaysLKP andYRKP down,the'normal'signal indication lamp |43 is displayed; Theshifting of leverLVA toits lposition extinguishes lamp |43 and afterpthere is' thesequencepf even'ts` of moving lever.' LV to its'l position, energizingthe control relay RKP;

shiftingof polarrelay HKPftoits left-hand'position andthe-subsequentenergizing 'of the-con trolrelaygLKP; the 'L signal indication-lampi isdisplayed.l When the sequence"V ofr eventsris lever LVV moved' to its rposition; controlrelay LKP picked. up; relayJH-KP' shifted to itsrig-hthandfposition, and the'subsequent picking upoi! thecontrol relayRKP, theV R1 signal indication lamp |45 is'displayed f The line Wire Lis' normally disconnectedfrom" the office" equipment at lthe frontcontact j|51 of a relayfLP; Relay LP Yis-en'ergized'by either one oftwocircuits. One circuit includes terminall B; backcontacts |581r and|591'of` relays NWE'and RWE, respectively, Windingiof relay LPtortheterminal'C, The'secon'd circuit can bertraced from the terminal -Bthrough front contact '|60fof the controlrelay LKPto 'the Winding ofrelay LP and thence toterrninal C; orbyfthe back 'contact |60 'of relayVLKPandthefront:

contact |6|o relayRKP'andas before traced. Itffoll'ows that whenevervthev push button PB is depressed to bring'about-'the,deenergizingof-'bothr the' switch indication" relays NWE and RWE, orv

when the; signallever LV1 is'operated to'eith'er itsl vo'r1 position' tobring about?y the. energizing of oneof'fthe Ycontrol relays RKP or LKP,the relay' is irrimediatelyV pickedv Tup' toV close the connection totheiline Wire L.

Although it' was stated earlierfinithespecication that'in this formv'ofapparatusof my invention alternating current is suppliedfrom'a com-Vadapted to alternating`V current suppliedlto thef'li oiiice station andto the eld station from separate and independent sources should it seemdesirable to do so. In Figs. 2a and 2b, there is provided standbyequipment at both the oflice station and at the field station thatautomatically makes available a local source of alternating current inthe event of a failure of the normal supply of power. As this standbyequipment is the same at both locations, except for difference infrequency, it is thought that a description of one will suiiice for anunderstanding of both. Referring to Fig. 2a, the power-olf relay POR hasits winding permanently connected across the terminals of the secondary|08 and is thus normally energized. The connection from the BX terminalof the secondary |08 to the office equipment includes the front contact|62 of the power-01T relay POR. A mechanically tuned alternator TA isnormally inactive but in the event there is a failure of the transformerT to supply current, the relay POR is deenergized to open the connectionfrom the secondary |08 to the ofce equipment and to render the tunedalternator active by the closing of its energizing cir-v cuit. Thisenergizing circuit includes the terminal B of a suitable source ofcurrent such as a storage battery not shown, back contact |63 of relayPOR, back Contact of its own armature |64, winding of the tunedalternator TA to the C terminal of the same source of current. As longas this circuit for the tuned alternator TA remains closed at contact|63, it is apparent that the armatures |64 and |65 will be oscillated atsome predetermined frequency as determined by their weight and by abiasing element customarily employed in such apparatus. When armature|65 engages its front contact, current is supplied to the left-hand halfof the primary winding |66 of a transformer 'Il and when armature |65engages its back contact, current is supplied to the right-hand half ofthe winding |66. This alternate energizing of the two halves of thewinding |66 induces an alternating current in the secondary winding |61of the transformer TI. Secondary |61 has one terminal connectedpermanently to the common return wire and its other terminal to the backcontact |62 of the power-off relay POR. It follows, that failure of thenormal source of current deenergizes relay POR to render the standbytuned alternator TA active and to complete a connection for supplyingthe oflce equipment with current from the secondary |61 of transformerTl. The tuned alternator TA may be any one of several types well knownin the art. A condenser |68 may be connected across the winding ofalternator TA and a condenser |69 connected across the primary winding|66.

While the tuned alternator TAI at the field station is preferably of thesame type as the tuned alternator TA and is controlled in a like mannerto supply current to the eld station equipment in the event of a failureof the transformer T at that location, I have found it to be desirableto have the two alternators deliver current of different frequencies andalso at a frequency different from the normal source of supply. Forexample, if the frequency of the normal source of supply is sixty cyclesper second, the frequency of the current supplied by TA and TAI may beone hundred forty and one hundred cycles per second, respectively.However, it will be understood that my invention is not confined to.these frequencies but they are given by way of illustration only.

To provide the despatcher with information pertaining to the occupancyof the approach track sections I provide the office station with a trackmodel TM on which are mounted a track indicating lamp |10 forreportingthe trafc condition of the approach track sections to the left of themain track section IT and ak lamp |1| for Ireporting the trafficcondition of the approach track sections` to the right of section IT.These lamps |10 and |1| are provided with simple circuits easily tracedwhich are controlled by relays RAP and LAP, respectively. Normally bothof these relays are deenergized and both lamps dark. A control circuitincluding a line wire L3 and the common return wire Com is provided forcontrolling the relays LAP and RAP by the iield station equipment. To beexplicit, the BX terminal of the secondary |08 at the iield station isconnected to the line wire L3 through a half-wave rectier |12 and theback contact |13 of the eastbound approach relay RAR, or through thehalf-wave rectifier |14 and the back contact 20 of the westboundapproach relay LAR or directly through the back contact |15 of therepeater relay TSP. Relays LAP and RAP each have one terminal of itswinding connected directly to the common return wire. The oppositeterminal of relay LAP is connected to the line L3 through the half-Waverectier |16 and the other terminal of the relay RAP is connected to theline wire L3 through half-wave rectifier |11. That these relays mayoperate at a lower voltage and to make them slightly slow-releasing, arectier |18 is connected across the terminals of the relay LAP and arectifier |19 across `the terminals of relay RAP. The rectiers |12 and|11 are so connected into the circuit that when the eastbound approachrelay RAR is deenergized to close the back co-ntact |13. half-wavepulses flow in the circuit to energize relay RAP and thus illuminate thetrack model lamp |10. In a similar manner the rectiers |14 and |16 areso connected into the circuit that when the westbound approach relay LARis deenergized to close the back contact 20, half-wave pulses ilow inthe line L3 to energize the relay LAP and thus illuminate the track lamp|1|. When the track repeater relay TSP is deenergized in response to atrain occupying the section IT and the back contact |15 is closed,full-wave alternating current is supplied to the line L3 and both relaysLAP and RAP are picked up to illuminate both lamps of the track model.In addition to the visible indication provided by the lamps |10 and |1|it is evident that the relays LAP and RAP can be arranged to controlaudible indication devices should it be thought desirable to do so.Furthermore, in place of having the track model normally dark and a lampdisplayed in response to an approach track section becoming occupied itcan be arranged to be normally illuminated and become dark as theapproach track sections are occupied.

In describing the operation of the apparatus shown in Figs. 2a, 2b and2U, I will assume the apparatus to be normally in the position shown inthe figures and I will rst consider the case where the despatcherdesires to reverse the switch SW and clear the signal LB to admit awestbound train into the siding PS. The despatcher will rst momentarilydepress the push button PB to pick up the relay PBR. Relay PBR on beingpicked up opens the stick circuit to the normal switch indication relayNWE and to the lamp |32 to deenergize that relay and to extinguish thenormalswitch indication lamp. Relay PBR also ropens at its back contact|25 the local loop circuits to the control relays LKP and RKP and closesat its front Vcontact |23V the connection from the BX terminal of Vthesecondary |08. Relay LP at once becomes energized, due to the fact thatboth relays NWE and RWE are now down, to close theconnection to the linewire L and thus full-wave alternating current is supplied 'to thecommunication channel during the slow-release period of the relay PBR.'Ihat is to say, an impulse of alternating current of a given durationis applied to the communica.- tion channel asI illustrated in thediagram a of Fig. 6, and this current impulse flows from the source atthe ofce station. As a result of this impulse of full-wave alternatingcurrent beingapplied to the communication channel the despatchercontrolled relays LGR and RGR of the field station are energized due tothe fact Vthat the traffic controlled circuit network is normallyclosed. To be explicit, this traffic controlled circuit net work can betraced from line wire L, through front contacts |80 and |8| of relaysITS and TSP, respectively, back contact |82 of the-time element relayTE, back contact |83 of relay |WR, and thence through the back contacts|85 and |86 of relays RAH and RBI-I, respectively, winding of relay LGR,rectifier |28 and to the common return wire Com, and also by the backcontacts |8'I and |88 of the relays LAH and LBH, respectively, windingof relay RGR and rectifier |29 to the common return wire.

` The'controlling current being a full-wave alterhereinbefore.

nating current, the rectifier |28 passes one-half of the wave toenergize relay LGR and the rectifier |29 p-asses the other half of thewave to energize the relay RGR. The energizing of both of the controlrelays LGR and RGR to simultaneously close both front contacts '|2 and13 completes the pick-up circuit for theV relay NWR inasmuch as theswitch controlling relay |WR isrnow in its normal positionand relay NWRnow picks ,upy to supply the relay |WR with current of reverse polarityas described in detail Relay |WR will be retained energized initsreverse position by its stick circuit and the motor M rendered active toreverse the of suflicient duration to operate relays LGR and RGR longenough that the relay NWR is picked up and relay |WR reversed. It is tobe noted -in connection with the circuit network for the relays LGR andRGR that the back contact 202 of relay KR will retain this networkclosed even after relay |WR has beenl energized to open its back contact|83.

When the switch is fully reversed, the switch indication relayl KR isenergized in its reverse position to close the short circuitv to thewinding of relay |WR causing that relay to be slowly released. Duringthe interval that the front contact |83 of relay |WR remains closedafter the switch indication relay KR is reversed the secondary |08 ofthe'transformer T at the iield station is connected to the lineY wire L,through the circuit network that includes rectier |3| as previouslyreferred to, to supply rectied current to the communication channel. TheVrectier |3| permits current to ilow only towards the BX terminal of thesecondary |08 and thus the indication current supplied consists ofhalf-wave pulses which flow from the CX terminal of the secondary |08 ofthe eld transformer over the common line Wire Com, wire |24, winding ofrelay RKP, rectifier |21, back contact |25, front Contact |51, line wireL, front contacts |80 yand |8|, back Contact |82, front contact |83 ofrelay |WR, front contact |90 and reverse polar contact |89 of relay KRand rectifier |3| to the BX terminal of secondary |08. With the controlrelay RKP of the oiiice loo-p circuit energized by this indicationcurrent, current will be supplied to the reverse switch indication relayRWE and that relay once picked up will then be retained energized by itsstick circuit and the reverse switch indication lamp |33 will beilluminated to indicate to the despatcherY that the switch is in thereverse position. The pick-up circuit for the reverse switch indicationrelayV RWE includes the back contact |34 of relay PBR, front contact |88of relay RKP and the back contact |39 of the normal switch indicationrelay NWE as previously pointed out, while the stick circuit for relayRWE includes the back contact |34, its own front contact |40 and theback contact |39.

The switch having thus been operated to its reverse position and areverse switch indication impulse returned to the office station toestab'- lish the reverse switch indication lamp |33, the despatcher nextmoves the lever LV to its l position to clear the signal LB. YThereverse switch indication relay RWE being now picked up and the ContactIS-I I4 closed the rectifier |22 permits half-wave pulses to be suppliedfrom the office secondary |08 to the office loop circuit that includesthe relay RKP and rectifier |2'| to energize the control relay RKP. Itis to be here noted that the reverse switch indication impulsetransmitted from the eld station terminated at the end of the releaseperiod of the relay |WR and the relays RKP and LP at the oiice sta-tionboth became deenergized. This office loop circuit closed as the lever LVis moved to its l position can be traced from the CX terminal of officesecondary |08, through wire |24, winding of relay RKP, rectifier |2l,back contact |25, contact ||3| |4, rectifier |22, front contact |42 ofrelay RWE and front contact |62 of relay POR to the BX terminal of thesecondary |08. With the energizing of relay RKP the circuit to the relayLP, that includes the front contact |6| of relay RKP, is closed and theconnectionto the line wire L is again completed so that the half-wavepulses now supplied at the oflice station will flow through thecommunication circuit and the corresponding of relay LGR, back contacts|86,|85, |83 and |82,V

and front contacts |8| and |80 of the traic controlled circuit network,line wire L, front contact |51, contact ||3| I4, rectifier Y |22, andfront contacts |42 and |62 to the BX terminal of the office secondary|08. Thus with the lever LV moved to its Z position current iscontinuously supplied from the ofce transformer T to retain the controlrelay RKP at the office station and the control relay LGR at the eldStation steadily energized in parallel. The polar varmatures of theswitch controlling relay IWR being now in the reverse position and theswitch indication relay KR being now energized in its reverse positionthe closing of the front contact 99 of the control relay LGR completesthe circuit to the signal controlling relay LBH and that relay is pickedup to clear the westbound signal LB.

The energizing of the signal controlling relay LBH not only clears thesignal LB but it also -closes the circuit for the indication currentfrom the secondary |08 of the eld transformer T that includes therectifier |30. The circuit for this return indication current extendsfrom lthe BX terminal of the field secondary |08 through rec- .tier |30,front contact |88 of relay LBH, back contacts |01, |83 and |82 and frontcontacts |8| and of the circuit network, line wire L, front contact |51,back contact |25, rectifier |26, winding of control relay LKP, wire |24and common :line wire Com to the CX terminal of the ield secondary |08.It will be recalled that the moving of the lever LV to its Z positionand the picking up of the relay RKP causes the polar relay HKP to beshifted to its left-hand position, and

thus the sequenceof moving the lever LV to its Z position, energizingthe control relay RKP, shifting relay HKP to its left-hand position andthe subsequent energizing of the relay LKP completes the circuit to theL signal indication lamp :|614 and that lamp will now be energized toindicate to the despatcher the clear position of the signal LB.Therefore, the despatcher now has before him a steady display of thereverse switch indication larnp i33 to indicate the reverse posiv tionof the switch SW and the continuous display of the signal indicationlampA |44 to indicate the clear position of the westbound signal LB. Itshould be noted that the energizing of the signal controlling relay LBHopens at its back contact 83 the connection to the control relay RGR andthus the half-wave pulses supplied by the eld equipment for indicationpurposes are prevented from operating the control relay RGR.

With'the apparatus in the condition just described, the transformer T atthe ofhce station continuously supplies through the rectifier |22. acontrol current consisting of half-wave pulses of the alternatingcurrent which retain the relay RKP at the oflice station energized andwhich ow over the common return wire through the rectifier |28 and therelay LGR and back over the line wire L to select the signal controllingrelay LBH forv clearing the signal LB. The fact that the relay LBH ispicked up permits an indication current, which consists of half-wavepulses, to flow from the field transformer T through rectifier |30towards the oiiice station over the line wire L through rectifier |26and relay LKP at the office station and back to the eld station over thecommon line wire.

The current in the communication channel is now a control currentconsisting of half-wave pulses of alternating current as illustrated bythe shady portion of. diagram d of Fig. 6 and an indication currentwhich consists of half-wave pulses of alternating current as illustratedby the unshaded portion of diagram d of Fig. 6. The control current andthe indication current both flow in the two line wires Com and L in thesame direction and are time-spaced apart a half cycle of the alternatingcurrent inasmuch as they are the opposite half waves of the alternatingcurrent supplied from the transmission line. Since this conditioninvolves 'proper polarities of trans- .former connections the conditionof the equipment is illustrated in Fig. 1. When the instantaneouspolarity of the secondary |08 of the office transformer T is as markedby the plus and minus signs, the instantaneous polarity of the secondary|08 of the field transformer T is as shown by the plus and minus signs.Consequently, any tendency of the current flowing from the positiveterminal of the field. transformer through rectifier |30, circuitnetwork, line wire L, controller LI, rectifier |22 and the secondaryM30-of the ofilce transformer is opposed by the voltage of the secondaryof the oifice transformer. It follows that there exists no flow of shortcircuit current of one secondary through the winding of the secondary ofthe other transformer. While this synchronization is advantageous, itwill be understood that it is not essential. As previously stated, whenthe standby tuned alternators are active, I have found it to bepreferable to have them diiferent in frequency and also each differentfrom the frequency of the normal source of current. In the cases ofsources of two differ'- ent frequencies the condition resulting during asignal operation would be that, the half-wave pulses applied to the linecircuit from the office source of energy to energize the control relayat the field station, and the half-wave pulses applied by the eld sourceof energy for indication would not be in synchronism and there would,therefore, be a tendency for a short circuit of. the two sources. Theactual condition in the line circuit at this time, if properresistances, such as resistances R|0 of Figs. 2a and 2b are inserted inthe circuit to prevent any short circuit current of damaging magnitude,would be current of irregular wave shape due to the combination of thetwo frequencies. As stated above, I havefound from tests that theapparatus works satisfactorily if frequencies be so selected that thedifference between the two frequencies is greater than the frequency ofpulses on which the operating relays would drop out.

I will now consider that a train approaches the switch from the rightshunting first the track relay A4TR and then the track relay 4TR of theapproach track sections A4T and 4T, respectively. The shunting of relayAllTR drops the approach relay LAR to close the back Contact 20 in theapproach indication circuit causing the energizing of the office relayLAP and the subsequent lighting up of the approach indication lamp onthe track model. When the signal controlling relay LBH was picked up toclear the signal LB, the stick circuit for the approach locking relayLMR was opened at the back contact 36 and that relay-y deenergized. Thedropping of the approach relay LAR by the westbound train entering thesection A4T opens the pick-up circuit for the relay LMR at the frontcontact 38 and the usual approach locking protection against thepossibility of a switch operation is provided.

When the westbound train arrives at the main track section IT, the trackrelay ITS is shunted, deenergizing in turn the repeater relay TSP.Dropping the relay ITS from its front to its back contacts causes amomentary interruption of the line circuit at they contact |80 but thisinterruption is of insufficient duration to drop either the controlrelay LGR or LKP since both of these relays are snubbed by rectiers.When relay TSP drops at the end of its slow-release period, the circuitto the signal controlling relay LBH is opened at the front contact 83and that relay is deenergized.A Deenergizing the relay LBH sets thesignal LB at stop and removes the supply of indication `energy from theline circuit by openingfthe 'front contact |88 and thus the oice controlrelay LKP drops extinguishing the L signal indication lamp |44 givingthe despatcher an indication of the time the westbound train arrivesY atthe main track section IT and also that the signal LB has been returnedto its stop position. The deenergizing of relay TSP also'closes at itsback' contactV |15 a direct connection between ,the secondary |08 andthe approach indication line wire L3 so that both relays LAP and RAP arepicked up and both lamps |10 and |1| on the track model displayed. Thusthe OS indication of the presence of a train on the main track sectionIT is accomplished by both the extinguishing of the L signal indicationlamp |44 and the illumination of the second lamp |10 on the track model.

If the operator returns the lever LV to its n gohqposition yimmediatelyfollowing the extinguishing ofthe lamp |44, the control energy isdiscontinued and both the office relay RKP and the eld relay LGR aredeenergized. Both the control relaysk LKP and RKP being now down, the

25 .normal signal indication lamp |43 is again displayed. As soon as thetrain advances far enough-.into the siding. to clear the approach tracksections, the approach relay LAR is reenergized and the approach lockingrelay LMR picked up to release the approach locking in the usual-manner.After the train has moved into the siding to clear the main tracksection IT, the track relay ITS is picked up as its pick-up circuit isnow closed at the back contacts 4 and 5 of relays LGR and RGR,respectively, and in turn the-repeater relay TSP is picked up at the endof itspick-up period. As soon as the relay TSP functions Yto open theback contact |15 in the approach'indication circuit both relays LAP andRAP become deenergized and both lamps on the track model areextinguished; `We now have the field equipment back in its normalposition with all .signals at stop andthe switch reversed, while at theoffice the reverse switch indication lamp 33 and the normal signalindication lamp |43 are-displayed indicating to the despatcher thiscondition of the switch and signals.

It is to be pointed out that the slow-release characteristics of relayTSP prevent-a momentary shunting of the track section IT, while theWestbound train occupies one of the approach Y sections, from releasingthe approach locking re- Y lay LMR in the event an opposing tracksection 5T or AST be occupied atvthe time. The slow pickup feature ofthe relay TSP prevents a momeneoyfnoted, Ythat contact 29.a permitsrelay LMR to pick up as this westbound train moves into the siding.

In the event the operator, instead of immediately returning the lever LVto its n position afterthe train arrives at the track section IT, leavesit remaining in its Z position, the track relay ITScould not be pickedup after the train has passed into the siding and cleared the section ITdue to the fact that its pick-up circuit is held open at the backcontact 4 of the control relay LGR as the controlenergy from the oflicecontinuesto hold relay LGR up. With track relay ITS remaining down, therepeater relay TSP remains vdeenergized and thefront contact 83 in a.circuitinetwork to .the signal .controlling relay LBH is `held open'topreventthe signal LB from again being lcleared as soon as the trainpasses oif'the section' IT. That is to say, there is provided azstickfeature for the signal LB that requires .the operator to first restorethe lever LV to its normal n position before the signal canbe clearedfor any following train. In connection Withthe retaining of the controlrelay LGR energizedin the event the operator leaves the lever LV at itsZposition after the westbound train has entered the section IT, it is tobe pointedfout that the circuit network for this controlling relay is atthis time completed at the back contact of relay ITS.

Let us next considerthe possibility of the operator depressing the pushbutton PB to restore the switch to its normal position immediately afterhe has replaced the lever LV in its n position and-before the train hasvacated the main track section |T. The relay PBR is picked up and fullwave alternating current supplied to the communication channel duringits slow-release period in the usual manner. While this alternatingcurrentY will energize both the control relays LGR andRGR at the fieldstation and in turn pick upthe relay RWR, the switch controlling relayIWR is prevented from operating due to the holding open of the frontcontacts 50 and 5| of relays ITS and TSP, respectively. At the end ofthe impulse of alternating current relays LGR and RGR together with therelay RWRl all become deenergized and thus no function is performed bythe iield equipment. At the oice the depressing of the push botton PBand the picking up of the relay PBR opens the stick circuit for therelay RWE and that relay is deenergized and the reverse switchindication lamp |33 extinguished, leaving the. operator without anyswitch indication. Both relays NWE and RWE now being down, the relay LPis held up holding closed the connection to the line circuit at itsfront contact |51. As soon as the train Vacates the section IT and,relay ITS picks up, a reverse switch indication impulse is supplied bythe iield equipment during the pick-up period of the relay TSP and thereverse switch indication relay RWE.

is reenergized 1 and the lamp |33 is reestablished to again indicate tothedespatcher the reverse position of the switch. Referring to Fig. 2b,when the train vacates the section |T and relay ITS is energized butbefore Vrelay TSP closes its front contact due to its slow pick-upcharacteristics,

the seco-ndary |08 of the field transformer supplies half-wave pulseswhich flow from the CX terminal over the common return wire Com,windingofrelay RKP, rectifier |21, back contact |25, front contact |51,line wire L, front contact Y front contact |98 and reverse contact |89of relay KR, rectifier |3| and to the BX terminal of sec-Y ondary |08.The energizing of the office relay RKP duringthe periodthat this reverseindication impulse persists permits the relay RWE to be picked upand1then retained energized by its stick circuit to reestablish thereverse switch indication lamp I 33; While there will occur a blinkingof the normal signal indication lamp |43 during the interval that therelay RKP is energized in thereestablishing of the reverse switchindication, that lamp is immediately again displayed as soon asthe'relay RKP drops at the end of the indication impulse. It followsthat although the despatcherhas attempted to make .a premature Vmovementofthe switch,.no operation takes place at .theeld station .aand heisagain provided with proper indications as soon as the track section ITis cleared.

In the event the despatcher restores lever LV to position n anddepresses the push button PB while the westbound train occupies one ofthe approach track sections and before it has reached the section IT,the switch controlling relay lWR is prevented from responding to theenergizing of the control relays LGR and RGR due to its circuit beingheld open at the front contact 49 of the approach locking relay LMR. Theoperator can regain control of the switch while the train occupies anapproach track section by setting the signal LB at stop, which he can doby moving lever LV back to its 1t position, and discontinue the supplyof energy to the relay LGR, and then operating the push button PB. Aslever LV is moved to its n position and relaysy RKP and LGR deenergized,the L signal indication lamp |44 is immediately extinguished, however,the normal signal indication lamp |43 will not light up until the signalcontrolling relay LBH has actually become deenergized to set the signalLB at stop due to the vfact that the iield apparatus will continue tosupply indication energy to the communication channel as long as relayLBH holds closed its front contacts. In actual practice the signalcontrolling relays may be made slow-releasing, especially in absolutepermissive block signaling systems, so there would be a considerabledelay in the signal actually assuming its stop position after the signallever LV was returned to its 11, position. The display of the normalsignal indication lamp |43 is thus an indication to the operator thatthe signal has actually assumed the stop position. The taking away ofthe signal LB from the westbound train starts the time element relay TEby virtue of the fact that the relay MP is picked up when the backContact 36 oi relay LBH closes. The operator in regaining control of theswitch will depress the push button PB immediately after he has restoredlever LV to the n position. While this operation of the push button PBcauses the relays LGR and RGR to be operated, it accomplishes nothing inthe control of the relay |WR as the circuit for that relay is now heldopen at the front contact i9 of the approach locking relay LMR, but itdoes cause the reverse switch indication lamp |33 to be extinguished.When the time element device TE has functioned to release the approachlocking, the fact is indicated to the operator by the reestablishing ofthe reverse switch indication lamp |33 in the following manner,providing, of course, the train has stopped short of the track sectionIT. At the expiration of the release period of the approach locking asdetermined by the time element relay TE, and after that relay has closedits front contacts, there will exist a switch indication circuit fromthe CX terminal of the eld secondary |98 over the common return wire,through the ofce loop circuit and back over the line wire L, aspreviously traced, thence through the front contacts iil and I8| ofrelays TS and TSP, respectively, front contact |82 of time element relayTE, front contact |99 and reverse contact |89 of relay KR, rectier I3|and to the BX terminal of the secondary H38. Thus during the intervalthat the relay TE holds its iront contacts closed, a reverse switchindication impulse will be supplied to the omce apparatus reestablishingthe indication lamp |33 which will indicate to the operator that thetime element device has functioned, the approach locking released andthat he has regained control over the switch. The operator can nowactuate the push button PB and bring about an operation of the switch SWin the usual manner. t

I will next assume that the apparatus is in 5 its normal position asshown in the iigures and the despatcher wishes to advance an eastboundtrain outl of the siding PS. The reversing of the switch SW will followthe operation of the push button PB in the manner already described. 10The operator will then move the lever LV to its r position closing thecontact ||6-I|1 of controller Rl permitting thereby half-wave pulses tobe supplied from the-office secondary |08 through rectifier |2|. Thesehalf-wave pulses 1 15 pass from the BX terminal through contact |62,front contact M2 of relay RWE, rectifier I2I, contact |6--I il, backcontact 25 of relay PBR, rectiiier |25, and winding of the relay LKR tothe CX terminal to energize that relay. As soon20 as the relay LP picksup to close the connection to the line wire L, the half-wave pulses aresupplied over the line wire L, the traiic controlled circuit network,winding of the relay RGR, rectifier |29 and back to the CX terminal orthet25 oce secondary Hi8 over the common return wire. The energizing ofthe control relay RGR closes the iront contact 97 in the circuit networkfor the signal controlling relay RBH and that relay is energized toclear the signal RB. When $30 relay RBI-I picks up, it closes the frontcontact |86 in the circuit network of the signal indication circuit andhalf-wave pulses flow from the iield secondary |98 over the commonreturn wire, relay RKP, rectiiier i2?, back contact |25, front.35contact l'i, line wire L, circuit network and rectiiier ISE to the BXterminal oi secondary |8. There is now present in the communicationchannel control half-wave pulses cwing from the oice station to theiield station, as il1us trated by the shaded portion of diagram e ofFig. 6, and indication half-wave pulses iiowing from the field stationto the onice station, as illustrated by the unshaded portion of diagrame of Fig. 6. As just pointed out, the control half; wave pulses effectthe energizing of relay RGR to clear the signal RB, and as the sequenceof moving lever LV to its r position, the energizing of relay LKP, andshifting of relay HKP to its right-hand position has selected thecircuit forthe lamp M5, the indication half-wave pulses by energizingthe relay RKP cause the display of the R signal indication lamp |45. Thepicking up of the relay RBB opens at back contact 26 the stick circuitfor the approach locking relay RMR causing the approach locking tofunction for the eastbound train in substantially the same manner thatthe approach locking functioned for the westbound train described above.The picking up of relay BH, also, opens at the backl contact |85 theloop circuit to relay LGR preventing the indication current fromenergizing that relay.

As the eastbound train enters the section IT and brings about thedeenergizing of relays TS and TSP, the R signal indication lamp |45 isextinguished to give an OS indication to the operator. The deenergizingof relay TSP also causes alternating current to be applied to theapproach indication circuit L3 and both lamps il@ and I'II of the trackmodel become illuminated. The train upon vacating the section |T willpermit the relay ITS to be reenergized over its pick-up circuit if theoperator has in the meantime replaced the lever LV back to its nposition to remove the

